FILE - In this June 6, 2011 file picture, the logo of Swiss drugmaker Roche is photographed in Rotkreuz, Switzerland. Roche Holding AG . Swiss pharmaceutical company Roche says it will buy InterMune, Inc., a California-based developer of treatments for lung diseases, in a deal worth US $8.3 billion. Roche said SundayAug. 24, 2014 the companies have reached an agreement under which Roche will acquire InterMune in an all-cash transaction, with Roche paying US$ 74.00 per InterMune share. That's a premium of 38 percent over InterMune's closing price on Friday. (AP Photo/Keystone/Urs Flueeler, File)

Photo: Urs Flueeler, Associated Press

FILE - In this June 6, 2011 file picture, the logo of Swiss...

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InterMune Inc. signage is displayed outside of the company's headquarters in Brisbane, California, U.S., on Friday, Aug. 15, 2014. Some of Europe's biggest drugmakers, including Sanofi and Roche Holding AG, are among bidders for U.S. biotechnology company InterMune Inc., people with knowledge of the matter said. Photographer: David Paul Morris/Bloomberg

Roche has agreed to acquire InterMune at $74 per share in an all-cash transaction, a price 38 percent higher than the company's $53.80 closing price on Friday.

The acquisition comes as InterMune is expected to win a long-coveted approval in the United States for pirfenidone, its medicine for the rare and fatal lung disease known as idiopathic pulmonary fibrosis. The disease has no known cause or cure and causes tissue deep in the lungs to become thick and scarred over time, making it hard to breathe. It affects about 128,100 people in the United States and kills about 40,000 people annually.

The drug is already approved in the European Union and Canada. But in the U.S., the Food and Drug Administration rejected pirfenidone in 2010 because it did not show benefit in a study. After the company came back with positive data from a new trial in February, the FDA designated pirfenidone a breakthrough therapy in July and is expediting its review. The deadline for the agency's decision is Nov. 23. Wells Fargo Co. estimates the drug could surpass $1 billion in global revenue by 2019.

Roche already sells two medicines for respiratory diseases, Pulmozyme and Xolair. It was one of several companies rumored to be bidding on InterMune, including Sanofi, GlaxoSmithKline and Actelion, Bloomberg has reported.

"This merger recognizes the significant value created by our team's commitment, hard work and execution for more than a decade to develop and commercialize treatment options for IPF patients and their families," InterMune Chairman and CEO Dan Welch said in a statement. "Roche shares our passion and commitment to the IPF community and to ensuring that pirfenidone is available as quickly as possible to patients in the United States, pending FDA approval."